The field of the present disclosure relates generally to turbine engines and, more specifically, to a fuel nozzle for use in a turbine engine.
Rotary machines, such as gas turbines, are often used to generate power for electric generators. Gas turbines, for example, have a gas path which typically includes, in serial-flow relationship, an air intake, a compressor, a combustor, a turbine, and a gas outlet. Compressor and turbine sections include at least one row of circumferentially-spaced rotating buckets or blades coupled within a housing. At least some known turbine engines are used in cogeneration facilities and power plants. Such engines may have high specific work and power per unit mass flow requirements. To increase operating efficiency, at least some known gas turbine engines may operate at increased combustion temperatures.
While operating known turbine engines at higher temperatures increases operating efficiency, it may also increase the generation of polluting emissions, such as oxides of nitrogen (NOX). Such emissions are generally undesirable and may be harmful to the environment. To facilitate reducing NOx emissions, at least some known gas turbine plants use selective catalytic reduction (SCR) systems. Known SCR systems convert NOx, with the aid of a catalyst, into elemental nitrogen and water. However, SCR systems increase the overall costs associated with turbine operation. Furthermore, at least some known gas turbine plants inject water into the fuel/air mixture prior to combustion to facilitate reducing combustion temperature. However, the presence of water in the turbine engine may result in damage to engine components such as turbine blades and the combustion liner.
At least some known fuel injection assemblies attempt to reduce NOx emissions by using pre-mixing technology. In such assemblies, a portion of fuel and air is mixed upstream from the combustor to produce a lean mixture. Pre-mixing the fuel and air facilitates controlling the temperature of the combustion gases such that the temperature does not rise above a threshold where NOx emissions are formed. Some known fuel injection assemblies include at least one set of vanes that are used to swirl fuel and air prior to use in a combustor. Such known assemblies are known as a “swozzle”. Other known fuel injection assemblies include perforated tubes that mix fuel and air therein.